ABSTRACT
Introduction: Long term symptoms following COVID-19 now affects a large number of patients. Fatigue, functional impairment, muscle weakness, and myalgia are among the most prevalent described symptoms. Routine investigations are often normal despite persisting symptoms. We previously found myopathic changes at electrophysiological examinations of 11 of 20 post-COVID-19 patients referred for investigation due to paresthesia (1) and we showed pathology in muscle biopsies from 16 patients (2). We here describe electromyography (EMG) results in post-COVID-19 patients with neuromuscular symptoms. Method(s): At the Post-COVID Clinic at Aarhus University Hospital patients are evaluated due to complex and persistent symptoms. From September 2020 to September 2021, 467 patients were evaluated of which 394 (84%) reported physical fatigue, muscle exhaustion, myalgia, and/or had reduced muscle strength. In case these symptoms were non-improving or affected daily function, patients were referred for EMG and single fiber EMG (sfEMG). Neurophysiological results were compared with 40 healthy subjects. Result(s): Currently a total of 85 patients had EMG investigation performed. 18 patients were not included in analyses due to comorbidities or insufficient investigations. Demographic and clinical characteristics did not differ comparing 67 included patients with all 467 patients. At a median of 8 (IQR 5-11) months, after the acute phase of COVID-19, EMG showed myopathic changes in 42 patients (63%) in biceps-brachii, 31 patients (46%) in anterior-tibial, and in 25 patients (37%) in vastus-medialis muscles. SfEMG showed increased mean jitter in 13 patients (19%) in tibialis-anterior with or without myopathic changes. sfEMG was performed in extensor-digitorum-communis muscle in 41 patients, and of these, 15 patients had increased jitter (37%). Conclusion(s): Myopathic changes are commonly seen in post-COVID-19 patients with neuromuscular symptoms. Abnormal sfEMG suggesting neuromuscular transmission defect is also seen with or without myopathic changes. These findings can potentially explain fatigue in post-COVID-19 patients. Copyright © 2022
ABSTRACT
OBJECTIVE: To investigate the peripheral nerve and muscle function electrophysiologically in patients with persistent neuromuscular symptoms following Coronavirus disease 2019 (COVID-19). METHODS: Twenty consecutive patients from a Long-term COVID-19 Clinic referred to electrophysiological examination with the suspicion of mono- or polyneuropathy were included. Examinations were performed from 77 to 255 (median: 216) days after acute COVID-19. None of the patients had received treatment at the intensive care unit. Of these, 10 patients were not even hospitalized. Conventional nerve conduction studies (NCS) and quantitative electromyography (qEMG) findings from three muscles were compared with 20 age- and sex-matched healthy controls. RESULTS: qEMG showed myopathic changes in one or more muscles in 11 patients (55%). Motor unit potential duration was shorter in patients compared to healthy controls in biceps brachii (10.02 ± 0.28 vs 11.75 ± 0.21), vastus medialis (10.86 ± 0.37 vs 12.52 ± 0.19) and anterior tibial (11.76 ± 0.31 vs 13.26 ± 0.21) muscles. All patients with myopathic qEMG reported about physical fatigue and 8 patients about myalgia while 3 patients without myopathic changes complained about physical fatigue. CONCLUSIONS: Long-term COVID-19 does not cause large fibre neuropathy, but myopathic changes are seen. SIGNIFICANCE: Myopathy may be an important cause of physical fatigue in long-term COVID-19 even in non-hospitalized patients.